Make a field in a dialog mandatory

I have made a dialog participant step. I want to make some fields in the dialog as mandatory. The property mandatory I guess works only for some xtypes such as textfield but it doesnt work for xtypes such as datefield etc. I have a requirement to make a datefield mandatory. Is there any way we can do it.

Any pointers will be greatly appreciated.

Thanks is advance

Ankush Dhingra